Subscriber line interface circuits may be found in a central office exchange of a telecommunications network. A subscriber line interface circuit (SLIC) provides a communications interface between a digital switching network of the central office and an analog subscriber line. The subscriber line may include a tip line and a ring line. The analog subscriber line connects the SLIC to subscriber equipment, such as a telephone.
The SLIC may communicate data signals, control signals, or both to the subscriber equipment. A ringing signal is an example of a subscriber equipment control signal that uses a relatively high voltage and current as compared to a voice band data signals. In some examples, the SLIC may provide a sinusoidal or trapezoidal ringing signal to the subscriber equipment.